This project represents an on-going study of the mechanical and electrical properties of the normal and diseased heart. Current efforts are directed in three general areas: 1) an evaluation of systolic performance of the diseased human ventricle with particular reference to the role of the diastolic properties of the ventricle. This includes a prospective study of chronic volume overload utilizing both non-invasive (echocardiographic) technics and invasive methods (pressure- volume relations). 2) A study of the electrophysiological abnormalities of the dog heart during coronary ligation and particularly following ligature release utilizing computerized technics for measuring excitation thresholds, dispersion of the refractory period, conduction times and strength-interval curves. 3) An evaluation of the use of external counterpulsation in the treatment of acute and chronic coronary heart disease. With regard to the former (acute coronary heart disease), the effects of diastolic augmentation (external counterpulsation) and systolic unloading (nitroprusside) are currently under investigation.